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1/*
2 * trace irqs off critical timings
3 *
4 * Copyright (C) 2007-2008 Steven Rostedt <srostedt@redhat.com>
5 * Copyright (C) 2008 Ingo Molnar <mingo@redhat.com>
6 *
7 * From code in the latency_tracer, that is:
8 *
9 * Copyright (C) 2004-2006 Ingo Molnar
10 * Copyright (C) 2004 Nadia Yvette Chambers
11 */
12#include <linux/kallsyms.h>
13#include <linux/uaccess.h>
14#include <linux/module.h>
15#include <linux/ftrace.h>
16
17#include "trace.h"
18
19static struct trace_array *irqsoff_trace __read_mostly;
20static int tracer_enabled __read_mostly;
21
22static DEFINE_PER_CPU(int, tracing_cpu);
23
24static DEFINE_RAW_SPINLOCK(max_trace_lock);
25
26enum {
27 TRACER_IRQS_OFF = (1 << 1),
28 TRACER_PREEMPT_OFF = (1 << 2),
29};
30
31static int trace_type __read_mostly;
32
33static int save_flags;
34
35static void stop_irqsoff_tracer(struct trace_array *tr, int graph);
36static int start_irqsoff_tracer(struct trace_array *tr, int graph);
37
38#ifdef CONFIG_PREEMPT_TRACER
39static inline int
40preempt_trace(void)
41{
42 return ((trace_type & TRACER_PREEMPT_OFF) && preempt_count());
43}
44#else
45# define preempt_trace() (0)
46#endif
47
48#ifdef CONFIG_IRQSOFF_TRACER
49static inline int
50irq_trace(void)
51{
52 return ((trace_type & TRACER_IRQS_OFF) &&
53 irqs_disabled());
54}
55#else
56# define irq_trace() (0)
57#endif
58
59#ifdef CONFIG_FUNCTION_GRAPH_TRACER
60static int irqsoff_display_graph(struct trace_array *tr, int set);
61# define is_graph(tr) ((tr)->trace_flags & TRACE_ITER_DISPLAY_GRAPH)
62#else
63static inline int irqsoff_display_graph(struct trace_array *tr, int set)
64{
65 return -EINVAL;
66}
67# define is_graph(tr) false
68#endif
69
70/*
71 * Sequence count - we record it when starting a measurement and
72 * skip the latency if the sequence has changed - some other section
73 * did a maximum and could disturb our measurement with serial console
74 * printouts, etc. Truly coinciding maximum latencies should be rare
75 * and what happens together happens separately as well, so this doesn't
76 * decrease the validity of the maximum found:
77 */
78static __cacheline_aligned_in_smp unsigned long max_sequence;
79
80#ifdef CONFIG_FUNCTION_TRACER
81/*
82 * Prologue for the preempt and irqs off function tracers.
83 *
84 * Returns 1 if it is OK to continue, and data->disabled is
85 * incremented.
86 * 0 if the trace is to be ignored, and data->disabled
87 * is kept the same.
88 *
89 * Note, this function is also used outside this ifdef but
90 * inside the #ifdef of the function graph tracer below.
91 * This is OK, since the function graph tracer is
92 * dependent on the function tracer.
93 */
94static int func_prolog_dec(struct trace_array *tr,
95 struct trace_array_cpu **data,
96 unsigned long *flags)
97{
98 long disabled;
99 int cpu;
100
101 /*
102 * Does not matter if we preempt. We test the flags
103 * afterward, to see if irqs are disabled or not.
104 * If we preempt and get a false positive, the flags
105 * test will fail.
106 */
107 cpu = raw_smp_processor_id();
108 if (likely(!per_cpu(tracing_cpu, cpu)))
109 return 0;
110
111 local_save_flags(*flags);
112 /*
113 * Slight chance to get a false positive on tracing_cpu,
114 * although I'm starting to think there isn't a chance.
115 * Leave this for now just to be paranoid.
116 */
117 if (!irqs_disabled_flags(*flags) && !preempt_count())
118 return 0;
119
120 *data = per_cpu_ptr(tr->trace_buffer.data, cpu);
121 disabled = atomic_inc_return(&(*data)->disabled);
122
123 if (likely(disabled == 1))
124 return 1;
125
126 atomic_dec(&(*data)->disabled);
127
128 return 0;
129}
130
131/*
132 * irqsoff uses its own tracer function to keep the overhead down:
133 */
134static void
135irqsoff_tracer_call(unsigned long ip, unsigned long parent_ip,
136 struct ftrace_ops *op, struct pt_regs *pt_regs)
137{
138 struct trace_array *tr = irqsoff_trace;
139 struct trace_array_cpu *data;
140 unsigned long flags;
141
142 if (!func_prolog_dec(tr, &data, &flags))
143 return;
144
145 trace_function(tr, ip, parent_ip, flags, preempt_count());
146
147 atomic_dec(&data->disabled);
148}
149#endif /* CONFIG_FUNCTION_TRACER */
150
151#ifdef CONFIG_FUNCTION_GRAPH_TRACER
152static int irqsoff_display_graph(struct trace_array *tr, int set)
153{
154 int cpu;
155
156 if (!(is_graph(tr) ^ set))
157 return 0;
158
159 stop_irqsoff_tracer(irqsoff_trace, !set);
160
161 for_each_possible_cpu(cpu)
162 per_cpu(tracing_cpu, cpu) = 0;
163
164 tr->max_latency = 0;
165 tracing_reset_online_cpus(&irqsoff_trace->trace_buffer);
166
167 return start_irqsoff_tracer(irqsoff_trace, set);
168}
169
170static int irqsoff_graph_entry(struct ftrace_graph_ent *trace)
171{
172 struct trace_array *tr = irqsoff_trace;
173 struct trace_array_cpu *data;
174 unsigned long flags;
175 int ret;
176 int pc;
177
178 if (ftrace_graph_ignore_func(trace))
179 return 0;
180 /*
181 * Do not trace a function if it's filtered by set_graph_notrace.
182 * Make the index of ret stack negative to indicate that it should
183 * ignore further functions. But it needs its own ret stack entry
184 * to recover the original index in order to continue tracing after
185 * returning from the function.
186 */
187 if (ftrace_graph_notrace_addr(trace->func))
188 return 1;
189
190 if (!func_prolog_dec(tr, &data, &flags))
191 return 0;
192
193 pc = preempt_count();
194 ret = __trace_graph_entry(tr, trace, flags, pc);
195 atomic_dec(&data->disabled);
196
197 return ret;
198}
199
200static void irqsoff_graph_return(struct ftrace_graph_ret *trace)
201{
202 struct trace_array *tr = irqsoff_trace;
203 struct trace_array_cpu *data;
204 unsigned long flags;
205 int pc;
206
207 if (!func_prolog_dec(tr, &data, &flags))
208 return;
209
210 pc = preempt_count();
211 __trace_graph_return(tr, trace, flags, pc);
212 atomic_dec(&data->disabled);
213}
214
215static void irqsoff_trace_open(struct trace_iterator *iter)
216{
217 if (is_graph(iter->tr))
218 graph_trace_open(iter);
219
220}
221
222static void irqsoff_trace_close(struct trace_iterator *iter)
223{
224 if (iter->private)
225 graph_trace_close(iter);
226}
227
228#define GRAPH_TRACER_FLAGS (TRACE_GRAPH_PRINT_CPU | \
229 TRACE_GRAPH_PRINT_PROC | \
230 TRACE_GRAPH_PRINT_ABS_TIME | \
231 TRACE_GRAPH_PRINT_DURATION)
232
233static enum print_line_t irqsoff_print_line(struct trace_iterator *iter)
234{
235 /*
236 * In graph mode call the graph tracer output function,
237 * otherwise go with the TRACE_FN event handler
238 */
239 if (is_graph(iter->tr))
240 return print_graph_function_flags(iter, GRAPH_TRACER_FLAGS);
241
242 return TRACE_TYPE_UNHANDLED;
243}
244
245static void irqsoff_print_header(struct seq_file *s)
246{
247 struct trace_array *tr = irqsoff_trace;
248
249 if (is_graph(tr))
250 print_graph_headers_flags(s, GRAPH_TRACER_FLAGS);
251 else
252 trace_default_header(s);
253}
254
255static void
256__trace_function(struct trace_array *tr,
257 unsigned long ip, unsigned long parent_ip,
258 unsigned long flags, int pc)
259{
260 if (is_graph(tr))
261 trace_graph_function(tr, ip, parent_ip, flags, pc);
262 else
263 trace_function(tr, ip, parent_ip, flags, pc);
264}
265
266#else
267#define __trace_function trace_function
268
269#ifdef CONFIG_FUNCTION_TRACER
270static int irqsoff_graph_entry(struct ftrace_graph_ent *trace)
271{
272 return -1;
273}
274#endif
275
276static enum print_line_t irqsoff_print_line(struct trace_iterator *iter)
277{
278 return TRACE_TYPE_UNHANDLED;
279}
280
281static void irqsoff_trace_open(struct trace_iterator *iter) { }
282static void irqsoff_trace_close(struct trace_iterator *iter) { }
283
284#ifdef CONFIG_FUNCTION_TRACER
285static void irqsoff_graph_return(struct ftrace_graph_ret *trace) { }
286static void irqsoff_print_header(struct seq_file *s)
287{
288 trace_default_header(s);
289}
290#else
291static void irqsoff_print_header(struct seq_file *s)
292{
293 trace_latency_header(s);
294}
295#endif /* CONFIG_FUNCTION_TRACER */
296#endif /* CONFIG_FUNCTION_GRAPH_TRACER */
297
298/*
299 * Should this new latency be reported/recorded?
300 */
301static bool report_latency(struct trace_array *tr, u64 delta)
302{
303 if (tracing_thresh) {
304 if (delta < tracing_thresh)
305 return false;
306 } else {
307 if (delta <= tr->max_latency)
308 return false;
309 }
310 return true;
311}
312
313static void
314check_critical_timing(struct trace_array *tr,
315 struct trace_array_cpu *data,
316 unsigned long parent_ip,
317 int cpu)
318{
319 u64 T0, T1, delta;
320 unsigned long flags;
321 int pc;
322
323 T0 = data->preempt_timestamp;
324 T1 = ftrace_now(cpu);
325 delta = T1-T0;
326
327 local_save_flags(flags);
328
329 pc = preempt_count();
330
331 if (!report_latency(tr, delta))
332 goto out;
333
334 raw_spin_lock_irqsave(&max_trace_lock, flags);
335
336 /* check if we are still the max latency */
337 if (!report_latency(tr, delta))
338 goto out_unlock;
339
340 __trace_function(tr, CALLER_ADDR0, parent_ip, flags, pc);
341 /* Skip 5 functions to get to the irq/preempt enable function */
342 __trace_stack(tr, flags, 5, pc);
343
344 if (data->critical_sequence != max_sequence)
345 goto out_unlock;
346
347 data->critical_end = parent_ip;
348
349 if (likely(!is_tracing_stopped())) {
350 tr->max_latency = delta;
351 update_max_tr_single(tr, current, cpu);
352 }
353
354 max_sequence++;
355
356out_unlock:
357 raw_spin_unlock_irqrestore(&max_trace_lock, flags);
358
359out:
360 data->critical_sequence = max_sequence;
361 data->preempt_timestamp = ftrace_now(cpu);
362 __trace_function(tr, CALLER_ADDR0, parent_ip, flags, pc);
363}
364
365static inline void
366start_critical_timing(unsigned long ip, unsigned long parent_ip)
367{
368 int cpu;
369 struct trace_array *tr = irqsoff_trace;
370 struct trace_array_cpu *data;
371 unsigned long flags;
372
373 if (!tracer_enabled || !tracing_is_enabled())
374 return;
375
376 cpu = raw_smp_processor_id();
377
378 if (per_cpu(tracing_cpu, cpu))
379 return;
380
381 data = per_cpu_ptr(tr->trace_buffer.data, cpu);
382
383 if (unlikely(!data) || atomic_read(&data->disabled))
384 return;
385
386 atomic_inc(&data->disabled);
387
388 data->critical_sequence = max_sequence;
389 data->preempt_timestamp = ftrace_now(cpu);
390 data->critical_start = parent_ip ? : ip;
391
392 local_save_flags(flags);
393
394 __trace_function(tr, ip, parent_ip, flags, preempt_count());
395
396 per_cpu(tracing_cpu, cpu) = 1;
397
398 atomic_dec(&data->disabled);
399}
400
401static inline void
402stop_critical_timing(unsigned long ip, unsigned long parent_ip)
403{
404 int cpu;
405 struct trace_array *tr = irqsoff_trace;
406 struct trace_array_cpu *data;
407 unsigned long flags;
408
409 cpu = raw_smp_processor_id();
410 /* Always clear the tracing cpu on stopping the trace */
411 if (unlikely(per_cpu(tracing_cpu, cpu)))
412 per_cpu(tracing_cpu, cpu) = 0;
413 else
414 return;
415
416 if (!tracer_enabled || !tracing_is_enabled())
417 return;
418
419 data = per_cpu_ptr(tr->trace_buffer.data, cpu);
420
421 if (unlikely(!data) ||
422 !data->critical_start || atomic_read(&data->disabled))
423 return;
424
425 atomic_inc(&data->disabled);
426
427 local_save_flags(flags);
428 __trace_function(tr, ip, parent_ip, flags, preempt_count());
429 check_critical_timing(tr, data, parent_ip ? : ip, cpu);
430 data->critical_start = 0;
431 atomic_dec(&data->disabled);
432}
433
434/* start and stop critical timings used to for stoppage (in idle) */
435void start_critical_timings(void)
436{
437 if (preempt_trace() || irq_trace())
438 start_critical_timing(CALLER_ADDR0, CALLER_ADDR1);
439}
440EXPORT_SYMBOL_GPL(start_critical_timings);
441
442void stop_critical_timings(void)
443{
444 if (preempt_trace() || irq_trace())
445 stop_critical_timing(CALLER_ADDR0, CALLER_ADDR1);
446}
447EXPORT_SYMBOL_GPL(stop_critical_timings);
448
449#ifdef CONFIG_IRQSOFF_TRACER
450#ifdef CONFIG_PROVE_LOCKING
451void time_hardirqs_on(unsigned long a0, unsigned long a1)
452{
453 if (!preempt_trace() && irq_trace())
454 stop_critical_timing(a0, a1);
455}
456
457void time_hardirqs_off(unsigned long a0, unsigned long a1)
458{
459 if (!preempt_trace() && irq_trace())
460 start_critical_timing(a0, a1);
461}
462
463#else /* !CONFIG_PROVE_LOCKING */
464
465/*
466 * Stubs:
467 */
468
469void trace_softirqs_on(unsigned long ip)
470{
471}
472
473void trace_softirqs_off(unsigned long ip)
474{
475}
476
477inline void print_irqtrace_events(struct task_struct *curr)
478{
479}
480
481/*
482 * We are only interested in hardirq on/off events:
483 */
484void trace_hardirqs_on(void)
485{
486 if (!preempt_trace() && irq_trace())
487 stop_critical_timing(CALLER_ADDR0, CALLER_ADDR1);
488}
489EXPORT_SYMBOL(trace_hardirqs_on);
490
491void trace_hardirqs_off(void)
492{
493 if (!preempt_trace() && irq_trace())
494 start_critical_timing(CALLER_ADDR0, CALLER_ADDR1);
495}
496EXPORT_SYMBOL(trace_hardirqs_off);
497
498__visible void trace_hardirqs_on_caller(unsigned long caller_addr)
499{
500 if (!preempt_trace() && irq_trace())
501 stop_critical_timing(CALLER_ADDR0, caller_addr);
502}
503EXPORT_SYMBOL(trace_hardirqs_on_caller);
504
505__visible void trace_hardirqs_off_caller(unsigned long caller_addr)
506{
507 if (!preempt_trace() && irq_trace())
508 start_critical_timing(CALLER_ADDR0, caller_addr);
509}
510EXPORT_SYMBOL(trace_hardirqs_off_caller);
511
512#endif /* CONFIG_PROVE_LOCKING */
513#endif /* CONFIG_IRQSOFF_TRACER */
514
515#ifdef CONFIG_PREEMPT_TRACER
516void trace_preempt_on(unsigned long a0, unsigned long a1)
517{
518 if (preempt_trace() && !irq_trace())
519 stop_critical_timing(a0, a1);
520}
521
522void trace_preempt_off(unsigned long a0, unsigned long a1)
523{
524 if (preempt_trace() && !irq_trace())
525 start_critical_timing(a0, a1);
526}
527#endif /* CONFIG_PREEMPT_TRACER */
528
529#ifdef CONFIG_FUNCTION_TRACER
530static bool function_enabled;
531
532static int register_irqsoff_function(struct trace_array *tr, int graph, int set)
533{
534 int ret;
535
536 /* 'set' is set if TRACE_ITER_FUNCTION is about to be set */
537 if (function_enabled || (!set && !(tr->trace_flags & TRACE_ITER_FUNCTION)))
538 return 0;
539
540 if (graph)
541 ret = register_ftrace_graph(&irqsoff_graph_return,
542 &irqsoff_graph_entry);
543 else
544 ret = register_ftrace_function(tr->ops);
545
546 if (!ret)
547 function_enabled = true;
548
549 return ret;
550}
551
552static void unregister_irqsoff_function(struct trace_array *tr, int graph)
553{
554 if (!function_enabled)
555 return;
556
557 if (graph)
558 unregister_ftrace_graph();
559 else
560 unregister_ftrace_function(tr->ops);
561
562 function_enabled = false;
563}
564
565static int irqsoff_function_set(struct trace_array *tr, u32 mask, int set)
566{
567 if (!(mask & TRACE_ITER_FUNCTION))
568 return 0;
569
570 if (set)
571 register_irqsoff_function(tr, is_graph(tr), 1);
572 else
573 unregister_irqsoff_function(tr, is_graph(tr));
574 return 1;
575}
576#else
577static int register_irqsoff_function(struct trace_array *tr, int graph, int set)
578{
579 return 0;
580}
581static void unregister_irqsoff_function(struct trace_array *tr, int graph) { }
582static inline int irqsoff_function_set(struct trace_array *tr, u32 mask, int set)
583{
584 return 0;
585}
586#endif /* CONFIG_FUNCTION_TRACER */
587
588static int irqsoff_flag_changed(struct trace_array *tr, u32 mask, int set)
589{
590 struct tracer *tracer = tr->current_trace;
591
592 if (irqsoff_function_set(tr, mask, set))
593 return 0;
594
595#ifdef CONFIG_FUNCTION_GRAPH_TRACER
596 if (mask & TRACE_ITER_DISPLAY_GRAPH)
597 return irqsoff_display_graph(tr, set);
598#endif
599
600 return trace_keep_overwrite(tracer, mask, set);
601}
602
603static int start_irqsoff_tracer(struct trace_array *tr, int graph)
604{
605 int ret;
606
607 ret = register_irqsoff_function(tr, graph, 0);
608
609 if (!ret && tracing_is_enabled())
610 tracer_enabled = 1;
611 else
612 tracer_enabled = 0;
613
614 return ret;
615}
616
617static void stop_irqsoff_tracer(struct trace_array *tr, int graph)
618{
619 tracer_enabled = 0;
620
621 unregister_irqsoff_function(tr, graph);
622}
623
624static bool irqsoff_busy;
625
626static int __irqsoff_tracer_init(struct trace_array *tr)
627{
628 if (irqsoff_busy)
629 return -EBUSY;
630
631 save_flags = tr->trace_flags;
632
633 /* non overwrite screws up the latency tracers */
634 set_tracer_flag(tr, TRACE_ITER_OVERWRITE, 1);
635 set_tracer_flag(tr, TRACE_ITER_LATENCY_FMT, 1);
636
637 tr->max_latency = 0;
638 irqsoff_trace = tr;
639 /* make sure that the tracer is visible */
640 smp_wmb();
641
642 ftrace_init_array_ops(tr, irqsoff_tracer_call);
643
644 /* Only toplevel instance supports graph tracing */
645 if (start_irqsoff_tracer(tr, (tr->flags & TRACE_ARRAY_FL_GLOBAL &&
646 is_graph(tr))))
647 printk(KERN_ERR "failed to start irqsoff tracer\n");
648
649 irqsoff_busy = true;
650 return 0;
651}
652
653static void irqsoff_tracer_reset(struct trace_array *tr)
654{
655 int lat_flag = save_flags & TRACE_ITER_LATENCY_FMT;
656 int overwrite_flag = save_flags & TRACE_ITER_OVERWRITE;
657
658 stop_irqsoff_tracer(tr, is_graph(tr));
659
660 set_tracer_flag(tr, TRACE_ITER_LATENCY_FMT, lat_flag);
661 set_tracer_flag(tr, TRACE_ITER_OVERWRITE, overwrite_flag);
662 ftrace_reset_array_ops(tr);
663
664 irqsoff_busy = false;
665}
666
667static void irqsoff_tracer_start(struct trace_array *tr)
668{
669 tracer_enabled = 1;
670}
671
672static void irqsoff_tracer_stop(struct trace_array *tr)
673{
674 tracer_enabled = 0;
675}
676
677#ifdef CONFIG_IRQSOFF_TRACER
678static int irqsoff_tracer_init(struct trace_array *tr)
679{
680 trace_type = TRACER_IRQS_OFF;
681
682 return __irqsoff_tracer_init(tr);
683}
684static struct tracer irqsoff_tracer __read_mostly =
685{
686 .name = "irqsoff",
687 .init = irqsoff_tracer_init,
688 .reset = irqsoff_tracer_reset,
689 .start = irqsoff_tracer_start,
690 .stop = irqsoff_tracer_stop,
691 .print_max = true,
692 .print_header = irqsoff_print_header,
693 .print_line = irqsoff_print_line,
694 .flag_changed = irqsoff_flag_changed,
695#ifdef CONFIG_FTRACE_SELFTEST
696 .selftest = trace_selftest_startup_irqsoff,
697#endif
698 .open = irqsoff_trace_open,
699 .close = irqsoff_trace_close,
700 .allow_instances = true,
701 .use_max_tr = true,
702};
703# define register_irqsoff(trace) register_tracer(&trace)
704#else
705# define register_irqsoff(trace) do { } while (0)
706#endif
707
708#ifdef CONFIG_PREEMPT_TRACER
709static int preemptoff_tracer_init(struct trace_array *tr)
710{
711 trace_type = TRACER_PREEMPT_OFF;
712
713 return __irqsoff_tracer_init(tr);
714}
715
716static struct tracer preemptoff_tracer __read_mostly =
717{
718 .name = "preemptoff",
719 .init = preemptoff_tracer_init,
720 .reset = irqsoff_tracer_reset,
721 .start = irqsoff_tracer_start,
722 .stop = irqsoff_tracer_stop,
723 .print_max = true,
724 .print_header = irqsoff_print_header,
725 .print_line = irqsoff_print_line,
726 .flag_changed = irqsoff_flag_changed,
727#ifdef CONFIG_FTRACE_SELFTEST
728 .selftest = trace_selftest_startup_preemptoff,
729#endif
730 .open = irqsoff_trace_open,
731 .close = irqsoff_trace_close,
732 .allow_instances = true,
733 .use_max_tr = true,
734};
735# define register_preemptoff(trace) register_tracer(&trace)
736#else
737# define register_preemptoff(trace) do { } while (0)
738#endif
739
740#if defined(CONFIG_IRQSOFF_TRACER) && \
741 defined(CONFIG_PREEMPT_TRACER)
742
743static int preemptirqsoff_tracer_init(struct trace_array *tr)
744{
745 trace_type = TRACER_IRQS_OFF | TRACER_PREEMPT_OFF;
746
747 return __irqsoff_tracer_init(tr);
748}
749
750static struct tracer preemptirqsoff_tracer __read_mostly =
751{
752 .name = "preemptirqsoff",
753 .init = preemptirqsoff_tracer_init,
754 .reset = irqsoff_tracer_reset,
755 .start = irqsoff_tracer_start,
756 .stop = irqsoff_tracer_stop,
757 .print_max = true,
758 .print_header = irqsoff_print_header,
759 .print_line = irqsoff_print_line,
760 .flag_changed = irqsoff_flag_changed,
761#ifdef CONFIG_FTRACE_SELFTEST
762 .selftest = trace_selftest_startup_preemptirqsoff,
763#endif
764 .open = irqsoff_trace_open,
765 .close = irqsoff_trace_close,
766 .allow_instances = true,
767 .use_max_tr = true,
768};
769
770# define register_preemptirqsoff(trace) register_tracer(&trace)
771#else
772# define register_preemptirqsoff(trace) do { } while (0)
773#endif
774
775__init static int init_irqsoff_tracer(void)
776{
777 register_irqsoff(irqsoff_tracer);
778 register_preemptoff(preemptoff_tracer);
779 register_preemptirqsoff(preemptirqsoff_tracer);
780
781 return 0;
782}
783core_initcall(init_irqsoff_tracer);
1/*
2 * trace irqs off critical timings
3 *
4 * Copyright (C) 2007-2008 Steven Rostedt <srostedt@redhat.com>
5 * Copyright (C) 2008 Ingo Molnar <mingo@redhat.com>
6 *
7 * From code in the latency_tracer, that is:
8 *
9 * Copyright (C) 2004-2006 Ingo Molnar
10 * Copyright (C) 2004 William Lee Irwin III
11 */
12#include <linux/kallsyms.h>
13#include <linux/debugfs.h>
14#include <linux/uaccess.h>
15#include <linux/module.h>
16#include <linux/ftrace.h>
17#include <linux/fs.h>
18
19#include "trace.h"
20
21static struct trace_array *irqsoff_trace __read_mostly;
22static int tracer_enabled __read_mostly;
23
24static DEFINE_PER_CPU(int, tracing_cpu);
25
26static DEFINE_SPINLOCK(max_trace_lock);
27
28enum {
29 TRACER_IRQS_OFF = (1 << 1),
30 TRACER_PREEMPT_OFF = (1 << 2),
31};
32
33static int trace_type __read_mostly;
34
35static int save_lat_flag;
36
37static void stop_irqsoff_tracer(struct trace_array *tr, int graph);
38static int start_irqsoff_tracer(struct trace_array *tr, int graph);
39
40#ifdef CONFIG_PREEMPT_TRACER
41static inline int
42preempt_trace(void)
43{
44 return ((trace_type & TRACER_PREEMPT_OFF) && preempt_count());
45}
46#else
47# define preempt_trace() (0)
48#endif
49
50#ifdef CONFIG_IRQSOFF_TRACER
51static inline int
52irq_trace(void)
53{
54 return ((trace_type & TRACER_IRQS_OFF) &&
55 irqs_disabled());
56}
57#else
58# define irq_trace() (0)
59#endif
60
61#define TRACE_DISPLAY_GRAPH 1
62
63static struct tracer_opt trace_opts[] = {
64#ifdef CONFIG_FUNCTION_GRAPH_TRACER
65 /* display latency trace as call graph */
66 { TRACER_OPT(display-graph, TRACE_DISPLAY_GRAPH) },
67#endif
68 { } /* Empty entry */
69};
70
71static struct tracer_flags tracer_flags = {
72 .val = 0,
73 .opts = trace_opts,
74};
75
76#define is_graph() (tracer_flags.val & TRACE_DISPLAY_GRAPH)
77
78/*
79 * Sequence count - we record it when starting a measurement and
80 * skip the latency if the sequence has changed - some other section
81 * did a maximum and could disturb our measurement with serial console
82 * printouts, etc. Truly coinciding maximum latencies should be rare
83 * and what happens together happens separately as well, so this doesn't
84 * decrease the validity of the maximum found:
85 */
86static __cacheline_aligned_in_smp unsigned long max_sequence;
87
88#ifdef CONFIG_FUNCTION_TRACER
89/*
90 * Prologue for the preempt and irqs off function tracers.
91 *
92 * Returns 1 if it is OK to continue, and data->disabled is
93 * incremented.
94 * 0 if the trace is to be ignored, and data->disabled
95 * is kept the same.
96 *
97 * Note, this function is also used outside this ifdef but
98 * inside the #ifdef of the function graph tracer below.
99 * This is OK, since the function graph tracer is
100 * dependent on the function tracer.
101 */
102static int func_prolog_dec(struct trace_array *tr,
103 struct trace_array_cpu **data,
104 unsigned long *flags)
105{
106 long disabled;
107 int cpu;
108
109 /*
110 * Does not matter if we preempt. We test the flags
111 * afterward, to see if irqs are disabled or not.
112 * If we preempt and get a false positive, the flags
113 * test will fail.
114 */
115 cpu = raw_smp_processor_id();
116 if (likely(!per_cpu(tracing_cpu, cpu)))
117 return 0;
118
119 local_save_flags(*flags);
120 /* slight chance to get a false positive on tracing_cpu */
121 if (!irqs_disabled_flags(*flags))
122 return 0;
123
124 *data = tr->data[cpu];
125 disabled = atomic_inc_return(&(*data)->disabled);
126
127 if (likely(disabled == 1))
128 return 1;
129
130 atomic_dec(&(*data)->disabled);
131
132 return 0;
133}
134
135/*
136 * irqsoff uses its own tracer function to keep the overhead down:
137 */
138static void
139irqsoff_tracer_call(unsigned long ip, unsigned long parent_ip)
140{
141 struct trace_array *tr = irqsoff_trace;
142 struct trace_array_cpu *data;
143 unsigned long flags;
144
145 if (!func_prolog_dec(tr, &data, &flags))
146 return;
147
148 trace_function(tr, ip, parent_ip, flags, preempt_count());
149
150 atomic_dec(&data->disabled);
151}
152
153static struct ftrace_ops trace_ops __read_mostly =
154{
155 .func = irqsoff_tracer_call,
156 .flags = FTRACE_OPS_FL_GLOBAL,
157};
158#endif /* CONFIG_FUNCTION_TRACER */
159
160#ifdef CONFIG_FUNCTION_GRAPH_TRACER
161static int irqsoff_set_flag(u32 old_flags, u32 bit, int set)
162{
163 int cpu;
164
165 if (!(bit & TRACE_DISPLAY_GRAPH))
166 return -EINVAL;
167
168 if (!(is_graph() ^ set))
169 return 0;
170
171 stop_irqsoff_tracer(irqsoff_trace, !set);
172
173 for_each_possible_cpu(cpu)
174 per_cpu(tracing_cpu, cpu) = 0;
175
176 tracing_max_latency = 0;
177 tracing_reset_online_cpus(irqsoff_trace);
178
179 return start_irqsoff_tracer(irqsoff_trace, set);
180}
181
182static int irqsoff_graph_entry(struct ftrace_graph_ent *trace)
183{
184 struct trace_array *tr = irqsoff_trace;
185 struct trace_array_cpu *data;
186 unsigned long flags;
187 int ret;
188 int pc;
189
190 if (!func_prolog_dec(tr, &data, &flags))
191 return 0;
192
193 pc = preempt_count();
194 ret = __trace_graph_entry(tr, trace, flags, pc);
195 atomic_dec(&data->disabled);
196
197 return ret;
198}
199
200static void irqsoff_graph_return(struct ftrace_graph_ret *trace)
201{
202 struct trace_array *tr = irqsoff_trace;
203 struct trace_array_cpu *data;
204 unsigned long flags;
205 int pc;
206
207 if (!func_prolog_dec(tr, &data, &flags))
208 return;
209
210 pc = preempt_count();
211 __trace_graph_return(tr, trace, flags, pc);
212 atomic_dec(&data->disabled);
213}
214
215static void irqsoff_trace_open(struct trace_iterator *iter)
216{
217 if (is_graph())
218 graph_trace_open(iter);
219
220}
221
222static void irqsoff_trace_close(struct trace_iterator *iter)
223{
224 if (iter->private)
225 graph_trace_close(iter);
226}
227
228#define GRAPH_TRACER_FLAGS (TRACE_GRAPH_PRINT_CPU | \
229 TRACE_GRAPH_PRINT_PROC | \
230 TRACE_GRAPH_PRINT_ABS_TIME | \
231 TRACE_GRAPH_PRINT_DURATION)
232
233static enum print_line_t irqsoff_print_line(struct trace_iterator *iter)
234{
235 /*
236 * In graph mode call the graph tracer output function,
237 * otherwise go with the TRACE_FN event handler
238 */
239 if (is_graph())
240 return print_graph_function_flags(iter, GRAPH_TRACER_FLAGS);
241
242 return TRACE_TYPE_UNHANDLED;
243}
244
245static void irqsoff_print_header(struct seq_file *s)
246{
247 if (is_graph())
248 print_graph_headers_flags(s, GRAPH_TRACER_FLAGS);
249 else
250 trace_default_header(s);
251}
252
253static void
254__trace_function(struct trace_array *tr,
255 unsigned long ip, unsigned long parent_ip,
256 unsigned long flags, int pc)
257{
258 if (is_graph())
259 trace_graph_function(tr, ip, parent_ip, flags, pc);
260 else
261 trace_function(tr, ip, parent_ip, flags, pc);
262}
263
264#else
265#define __trace_function trace_function
266
267static int irqsoff_set_flag(u32 old_flags, u32 bit, int set)
268{
269 return -EINVAL;
270}
271
272static int irqsoff_graph_entry(struct ftrace_graph_ent *trace)
273{
274 return -1;
275}
276
277static enum print_line_t irqsoff_print_line(struct trace_iterator *iter)
278{
279 return TRACE_TYPE_UNHANDLED;
280}
281
282static void irqsoff_graph_return(struct ftrace_graph_ret *trace) { }
283static void irqsoff_print_header(struct seq_file *s) { }
284static void irqsoff_trace_open(struct trace_iterator *iter) { }
285static void irqsoff_trace_close(struct trace_iterator *iter) { }
286#endif /* CONFIG_FUNCTION_GRAPH_TRACER */
287
288/*
289 * Should this new latency be reported/recorded?
290 */
291static int report_latency(cycle_t delta)
292{
293 if (tracing_thresh) {
294 if (delta < tracing_thresh)
295 return 0;
296 } else {
297 if (delta <= tracing_max_latency)
298 return 0;
299 }
300 return 1;
301}
302
303static void
304check_critical_timing(struct trace_array *tr,
305 struct trace_array_cpu *data,
306 unsigned long parent_ip,
307 int cpu)
308{
309 cycle_t T0, T1, delta;
310 unsigned long flags;
311 int pc;
312
313 T0 = data->preempt_timestamp;
314 T1 = ftrace_now(cpu);
315 delta = T1-T0;
316
317 local_save_flags(flags);
318
319 pc = preempt_count();
320
321 if (!report_latency(delta))
322 goto out;
323
324 spin_lock_irqsave(&max_trace_lock, flags);
325
326 /* check if we are still the max latency */
327 if (!report_latency(delta))
328 goto out_unlock;
329
330 __trace_function(tr, CALLER_ADDR0, parent_ip, flags, pc);
331 /* Skip 5 functions to get to the irq/preempt enable function */
332 __trace_stack(tr, flags, 5, pc);
333
334 if (data->critical_sequence != max_sequence)
335 goto out_unlock;
336
337 data->critical_end = parent_ip;
338
339 if (likely(!is_tracing_stopped())) {
340 tracing_max_latency = delta;
341 update_max_tr_single(tr, current, cpu);
342 }
343
344 max_sequence++;
345
346out_unlock:
347 spin_unlock_irqrestore(&max_trace_lock, flags);
348
349out:
350 data->critical_sequence = max_sequence;
351 data->preempt_timestamp = ftrace_now(cpu);
352 __trace_function(tr, CALLER_ADDR0, parent_ip, flags, pc);
353}
354
355static inline void
356start_critical_timing(unsigned long ip, unsigned long parent_ip)
357{
358 int cpu;
359 struct trace_array *tr = irqsoff_trace;
360 struct trace_array_cpu *data;
361 unsigned long flags;
362
363 if (likely(!tracer_enabled))
364 return;
365
366 cpu = raw_smp_processor_id();
367
368 if (per_cpu(tracing_cpu, cpu))
369 return;
370
371 data = tr->data[cpu];
372
373 if (unlikely(!data) || atomic_read(&data->disabled))
374 return;
375
376 atomic_inc(&data->disabled);
377
378 data->critical_sequence = max_sequence;
379 data->preempt_timestamp = ftrace_now(cpu);
380 data->critical_start = parent_ip ? : ip;
381
382 local_save_flags(flags);
383
384 __trace_function(tr, ip, parent_ip, flags, preempt_count());
385
386 per_cpu(tracing_cpu, cpu) = 1;
387
388 atomic_dec(&data->disabled);
389}
390
391static inline void
392stop_critical_timing(unsigned long ip, unsigned long parent_ip)
393{
394 int cpu;
395 struct trace_array *tr = irqsoff_trace;
396 struct trace_array_cpu *data;
397 unsigned long flags;
398
399 cpu = raw_smp_processor_id();
400 /* Always clear the tracing cpu on stopping the trace */
401 if (unlikely(per_cpu(tracing_cpu, cpu)))
402 per_cpu(tracing_cpu, cpu) = 0;
403 else
404 return;
405
406 if (!tracer_enabled)
407 return;
408
409 data = tr->data[cpu];
410
411 if (unlikely(!data) ||
412 !data->critical_start || atomic_read(&data->disabled))
413 return;
414
415 atomic_inc(&data->disabled);
416
417 local_save_flags(flags);
418 __trace_function(tr, ip, parent_ip, flags, preempt_count());
419 check_critical_timing(tr, data, parent_ip ? : ip, cpu);
420 data->critical_start = 0;
421 atomic_dec(&data->disabled);
422}
423
424/* start and stop critical timings used to for stoppage (in idle) */
425void start_critical_timings(void)
426{
427 if (preempt_trace() || irq_trace())
428 start_critical_timing(CALLER_ADDR0, CALLER_ADDR1);
429}
430EXPORT_SYMBOL_GPL(start_critical_timings);
431
432void stop_critical_timings(void)
433{
434 if (preempt_trace() || irq_trace())
435 stop_critical_timing(CALLER_ADDR0, CALLER_ADDR1);
436}
437EXPORT_SYMBOL_GPL(stop_critical_timings);
438
439#ifdef CONFIG_IRQSOFF_TRACER
440#ifdef CONFIG_PROVE_LOCKING
441void time_hardirqs_on(unsigned long a0, unsigned long a1)
442{
443 if (!preempt_trace() && irq_trace())
444 stop_critical_timing(a0, a1);
445}
446
447void time_hardirqs_off(unsigned long a0, unsigned long a1)
448{
449 if (!preempt_trace() && irq_trace())
450 start_critical_timing(a0, a1);
451}
452
453#else /* !CONFIG_PROVE_LOCKING */
454
455/*
456 * Stubs:
457 */
458
459void trace_softirqs_on(unsigned long ip)
460{
461}
462
463void trace_softirqs_off(unsigned long ip)
464{
465}
466
467inline void print_irqtrace_events(struct task_struct *curr)
468{
469}
470
471/*
472 * We are only interested in hardirq on/off events:
473 */
474void trace_hardirqs_on(void)
475{
476 if (!preempt_trace() && irq_trace())
477 stop_critical_timing(CALLER_ADDR0, CALLER_ADDR1);
478}
479EXPORT_SYMBOL(trace_hardirqs_on);
480
481void trace_hardirqs_off(void)
482{
483 if (!preempt_trace() && irq_trace())
484 start_critical_timing(CALLER_ADDR0, CALLER_ADDR1);
485}
486EXPORT_SYMBOL(trace_hardirqs_off);
487
488void trace_hardirqs_on_caller(unsigned long caller_addr)
489{
490 if (!preempt_trace() && irq_trace())
491 stop_critical_timing(CALLER_ADDR0, caller_addr);
492}
493EXPORT_SYMBOL(trace_hardirqs_on_caller);
494
495void trace_hardirqs_off_caller(unsigned long caller_addr)
496{
497 if (!preempt_trace() && irq_trace())
498 start_critical_timing(CALLER_ADDR0, caller_addr);
499}
500EXPORT_SYMBOL(trace_hardirqs_off_caller);
501
502#endif /* CONFIG_PROVE_LOCKING */
503#endif /* CONFIG_IRQSOFF_TRACER */
504
505#ifdef CONFIG_PREEMPT_TRACER
506void trace_preempt_on(unsigned long a0, unsigned long a1)
507{
508 if (preempt_trace())
509 stop_critical_timing(a0, a1);
510}
511
512void trace_preempt_off(unsigned long a0, unsigned long a1)
513{
514 if (preempt_trace())
515 start_critical_timing(a0, a1);
516}
517#endif /* CONFIG_PREEMPT_TRACER */
518
519static int start_irqsoff_tracer(struct trace_array *tr, int graph)
520{
521 int ret = 0;
522
523 if (!graph)
524 ret = register_ftrace_function(&trace_ops);
525 else
526 ret = register_ftrace_graph(&irqsoff_graph_return,
527 &irqsoff_graph_entry);
528
529 if (!ret && tracing_is_enabled())
530 tracer_enabled = 1;
531 else
532 tracer_enabled = 0;
533
534 return ret;
535}
536
537static void stop_irqsoff_tracer(struct trace_array *tr, int graph)
538{
539 tracer_enabled = 0;
540
541 if (!graph)
542 unregister_ftrace_function(&trace_ops);
543 else
544 unregister_ftrace_graph();
545}
546
547static void __irqsoff_tracer_init(struct trace_array *tr)
548{
549 save_lat_flag = trace_flags & TRACE_ITER_LATENCY_FMT;
550 trace_flags |= TRACE_ITER_LATENCY_FMT;
551
552 tracing_max_latency = 0;
553 irqsoff_trace = tr;
554 /* make sure that the tracer is visible */
555 smp_wmb();
556 tracing_reset_online_cpus(tr);
557
558 if (start_irqsoff_tracer(tr, is_graph()))
559 printk(KERN_ERR "failed to start irqsoff tracer\n");
560}
561
562static void irqsoff_tracer_reset(struct trace_array *tr)
563{
564 stop_irqsoff_tracer(tr, is_graph());
565
566 if (!save_lat_flag)
567 trace_flags &= ~TRACE_ITER_LATENCY_FMT;
568}
569
570static void irqsoff_tracer_start(struct trace_array *tr)
571{
572 tracer_enabled = 1;
573}
574
575static void irqsoff_tracer_stop(struct trace_array *tr)
576{
577 tracer_enabled = 0;
578}
579
580#ifdef CONFIG_IRQSOFF_TRACER
581static int irqsoff_tracer_init(struct trace_array *tr)
582{
583 trace_type = TRACER_IRQS_OFF;
584
585 __irqsoff_tracer_init(tr);
586 return 0;
587}
588static struct tracer irqsoff_tracer __read_mostly =
589{
590 .name = "irqsoff",
591 .init = irqsoff_tracer_init,
592 .reset = irqsoff_tracer_reset,
593 .start = irqsoff_tracer_start,
594 .stop = irqsoff_tracer_stop,
595 .print_max = 1,
596 .print_header = irqsoff_print_header,
597 .print_line = irqsoff_print_line,
598 .flags = &tracer_flags,
599 .set_flag = irqsoff_set_flag,
600#ifdef CONFIG_FTRACE_SELFTEST
601 .selftest = trace_selftest_startup_irqsoff,
602#endif
603 .open = irqsoff_trace_open,
604 .close = irqsoff_trace_close,
605 .use_max_tr = 1,
606};
607# define register_irqsoff(trace) register_tracer(&trace)
608#else
609# define register_irqsoff(trace) do { } while (0)
610#endif
611
612#ifdef CONFIG_PREEMPT_TRACER
613static int preemptoff_tracer_init(struct trace_array *tr)
614{
615 trace_type = TRACER_PREEMPT_OFF;
616
617 __irqsoff_tracer_init(tr);
618 return 0;
619}
620
621static struct tracer preemptoff_tracer __read_mostly =
622{
623 .name = "preemptoff",
624 .init = preemptoff_tracer_init,
625 .reset = irqsoff_tracer_reset,
626 .start = irqsoff_tracer_start,
627 .stop = irqsoff_tracer_stop,
628 .print_max = 1,
629 .print_header = irqsoff_print_header,
630 .print_line = irqsoff_print_line,
631 .flags = &tracer_flags,
632 .set_flag = irqsoff_set_flag,
633#ifdef CONFIG_FTRACE_SELFTEST
634 .selftest = trace_selftest_startup_preemptoff,
635#endif
636 .open = irqsoff_trace_open,
637 .close = irqsoff_trace_close,
638 .use_max_tr = 1,
639};
640# define register_preemptoff(trace) register_tracer(&trace)
641#else
642# define register_preemptoff(trace) do { } while (0)
643#endif
644
645#if defined(CONFIG_IRQSOFF_TRACER) && \
646 defined(CONFIG_PREEMPT_TRACER)
647
648static int preemptirqsoff_tracer_init(struct trace_array *tr)
649{
650 trace_type = TRACER_IRQS_OFF | TRACER_PREEMPT_OFF;
651
652 __irqsoff_tracer_init(tr);
653 return 0;
654}
655
656static struct tracer preemptirqsoff_tracer __read_mostly =
657{
658 .name = "preemptirqsoff",
659 .init = preemptirqsoff_tracer_init,
660 .reset = irqsoff_tracer_reset,
661 .start = irqsoff_tracer_start,
662 .stop = irqsoff_tracer_stop,
663 .print_max = 1,
664 .print_header = irqsoff_print_header,
665 .print_line = irqsoff_print_line,
666 .flags = &tracer_flags,
667 .set_flag = irqsoff_set_flag,
668#ifdef CONFIG_FTRACE_SELFTEST
669 .selftest = trace_selftest_startup_preemptirqsoff,
670#endif
671 .open = irqsoff_trace_open,
672 .close = irqsoff_trace_close,
673 .use_max_tr = 1,
674};
675
676# define register_preemptirqsoff(trace) register_tracer(&trace)
677#else
678# define register_preemptirqsoff(trace) do { } while (0)
679#endif
680
681__init static int init_irqsoff_tracer(void)
682{
683 register_irqsoff(irqsoff_tracer);
684 register_preemptoff(preemptoff_tracer);
685 register_preemptirqsoff(preemptirqsoff_tracer);
686
687 return 0;
688}
689device_initcall(init_irqsoff_tracer);